(a) Field of the Invention
The present invention relates to a bench vise and more particularly to a micro-adjustable parallel bench vise, which allows micro-adjustment of the positions of multiple vises on one slide holder.
(b) Description of the Prior Art
A conventional parallel bench vise, as shown in FIGS. 1 and 2, includes a rack 10 having a series of teeth 101, a fixed jaw member 20 having a series of teeth 201 on its top side, a slope 202 on its one end and a clamping face 203 on its opposite end, a movable jaw member 30 having a slope 301 on its one end and a clamping face 302 on its opposite end, and a wedge block 40 set in between the slope 202 of the fixed jaw member 20 and the slope 301 of the movable jaw member 30. When forcing the wedge block 40 downwards, the movable jaw member 30 is moved along the rack 10 to clamp a workpiece 50.
According to the aforesaid prior art design, the teeth 101 of the rack 10 are meshed with the teeth 201 of the fixed jaw member 20. Theoretically, the pitch of the teeth 101 and the pitch of the teeth 201 must get the same precision. However, in actual practice, it is difficult to have the pitch of the teeth 101 and the pitch of the teeth 201 get the same precision. When multiple fixed jaw members 20, movable jaw members 30 and wedge blocks 40 are joined to parallel racks 10 for application, an error in coordinates will be inevitable. However, due to the limitation of minimum pitch of the teeth 101 and 201 (see P in FIG. 2), forward/backward micro-adjustment is not allowed. This is the major drawback of the aforesaid prior art design. Further, this prior art design uses the wedge block 40 to move the movable jaw member 30 in producing a clamping force. This clamping force is small. Further, the stroke of the movable jaw member 30 is short. Further, as shown in FIG. 1, a pad 60 must be added to the bottom side of the workpiece 50 during application, therefore it is difficult to keep the workpiece 50 in balance. Further, when forcing the wedge block 40 to move the movable jaw member 30, the movable jaw member 30 may be tilted. At this time, as shown in FIG. 3, the workpiece 50 tends to be biased, affecting workpiece processing precision.